The invention seeks to make the object capable of being powered externally, in particular to give access to the data memory in the event of the internal battery failing or being exhausted. The invention also relates to a method and to apparatus for externally powering such an object.
A particular (but non-limiting) example of an object of this type is a "contactless card" or a "contactless identity badge", i.e. a portable object suitable for interchanging information (by reading and possibly by writing in the data memory of the object) with an external reader by approaching the object thereto in such a manner as to enable electromagnetic coupling without direct contact. Data is then interchanged by radio or by varying a magnetic field produced by an induction coil.
The invention relates to objects powered by an internal battery, particularly objects that are discardable, and thus providing no physical access to the battery by opening a housing or a trap door.
When the battery comes to the end of its life or when it fails, the electronic circuit of the object detects a drop in voltage and warns the user that the end of battery life is near by a visual or audible warning, and then deactivates the electronic circuit to prevent it performing wrongly because of insufficient voltage.
Nevertheless, the data in the memory is conserved and is therefore intact, even though physically inaccessible given that the battery is exhausted so the object is no longer capable of communicating with the external reader--unlike unpowered identity badges, for example, which receive operating power from the reader while they are being read so that they constitute responders that are purely passive. In this situation, data is conserved either because the memory used is non-volatile, or else, more commonly, because the object switches to operating in a "degraded" mode in which, once the near end of battery life has been detected, the remaining energy is used solely for conserving the data in the memory with any external communication being prevented since that would consume too much energy and would imperil the integrity of the data in the memory.
A particular example of such portable objects comprises badges used for remote payment, in particular payment of fares for urban transport, e.g. by bus or by train.
The data memory is loaded with a certain amount of information, e.g. a certain number of units that can be decremented and that correspond to the value of a ride or to a monetary unit, or information relating to weekly, monthly, or annual season tickets.
It will be understood that important information remains in the data memory at the end of battery lifetime and that this information must be recovered in order to ensure the user does not lose any rights, e.g. by transferring the information into a new badge.
It is indeed possible to design a badge that can be opened to allow the battery to be changed. Nevertheless, that operation is difficult given the high degree of circuit miniaturization, and it turns out to be preferable to make badges of that type in the form of an object that has a long lifetime (typically several years), with a housing that is sealed and discardable once the battery is exhausted.